To meet the demand for wireless data traffic, which has increased since deployment of 4th-generation (4G) communication systems, efforts have been made to develop an improved 5th-generation (5G) or pre-5G communication system. Therefore, the 5G or pre-5G communication system is also called a ‘beyond 4G network’ or a ‘post long-term evolution (LTE) system’.
It is considered that the 5G communication system will be implemented in millimeter wave (mmWave) bands, e.g., 60 GHz bands, so as to accomplish higher data rates. To reduce propagation loss of radio waves and increase a transmission distance, a beam forming technique, a massive multiple-input multiple-output (MIMO) technique, a full dimensional MIMO (FD-MIMO) technique, an array antenna technique, an analog beam forming technique, and a large scale antenna technique are discussed in 5G communication systems.
In addition, in 5G communication systems, development for system network improvement is under way based on advanced small cells, cloud radio access networks (RANs), ultra-dense networks, a device-to-device (D2D) communication, a wireless backhaul, a moving network, a cooperative communication, coordinated multi-points (CoMP), reception-end interference cancellation, and the like.
In the 5G system, a hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) modulation (FQAM) and a sliding window superposition coding (SWSC) as an advanced coding and modulation (ACM) scheme, and a filter bank multi carrier (FBMC) scheme, a non-orthogonal multiple Access (NOMA) scheme, and a sparse code multiple access (SCMA) scheme as an advanced access technology have been developed.
In a communication system supporting a multi-user MIMO (MU-MIMO) scheme, each user equipment (UE) feeds back channel quality information based on a channel status between each UE and a base station (BS) for communication with the BS. For example, the channel quality information may be a channel quality index (CQI).
The BS determines a modulation and coding scheme (MCS) level for each UE based on the channel quality information fed back by each UE, and transmits data to each UE based on the MCS level.
Recently, in broadband carrier transmission using a mmWave band which has emerged as 5G communication, an array antenna is used as each transmission antenna (Tx antenna), so a beam gain may be acquired based on radio frequency (RF) beamforming. In this case, a UE performs a beam sweeping process for each Tx antenna, and selects an optimal Tx antenna and an optimal transmission beam (Tx beam) based on a result of the beam sweeping process.
In a communication system supporting a single-user MIMO (SU-MIMO) scheme, a UE knows a beam index for each of a plurality of Tx antennas included in a BS, so the UE may determine a CQI based on the beam index for each of the plurality of Tx antennas.
Alternatively, in a communication system supporting a MU-MIMO scheme, each UE knows only a beam index for a Tx antenna allocated to each UE among a plurality of Tx antennas included in a BS and does not know beam indexes for Tx antennas allocated to other UEs. Each UE does not know beam indexes for Tx antennas allocated to other UEs, so each UE may not detect interference due to beams for the Tx antennas allocated to the other UEs and determine a correct CQI.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.